Fuel control apparatus in combination with internal combustion engines generally include a throttle actuated butterfly valve for controlling the flow of air through a venturi. The venturi has associated therewith a fuel flow passageway located in the low pressure area thereof so that fuel can be sucked from a float chamber into the venturi in direct portion to the mass flow of air through the venturi.
The quantity of fuel which flows from the float chamber into the venturi is proportional to the liquid level contained within the float chamber. The complexity of this type carburetor depends upon the various different expedients employed in order to cause the fuel air ratio to approximate a constant value. Therefore, the closer the air fuel ratio approaches a constant value for all ranges of mass flow, the more expensive the carburetor becomes because of the various different complex fuel control devices which must be included therewith.
As air flows through a carburetor, there is a rapid drop in pressure across the butterfly valve thereof with there being a low pressure area effected immediately downstream of the butterfly valve. Others have proposed to utilize the relative motion between the butterfly valve and the valve body in order that a metered quantity of fuel proportional to the area between the butterfly valve and the valve body might be delivered thereby providing an acceptable air fuel ratio for most ranges of flow for the carburetor. For example, attention is directed to the following prior art which employs various different expedients for attaining this type of fuel system:
Maxwell 795,357; Shakespeare 1,129,129; Rhoads 1,305,744; Wasserlein 1,374,262; Eiker 1,718,735; Kennedy 3,341,185; Firth 2,190,314; Kennedy 2,995,349; Brandwood 3,202,404.
As evidenced by the foregoing prior art patents, fuel flow devices of the above type are extremely complex in operation and require numerous different moving parts so that the resulting apparatus is expensive in initial cost and difficult to maintain. It would, therefore, be desirable to significantly simplify fuel flow apparatus of this type so that the resulting device requires a minimum number of co-acting parts and the initial cost thereof is nominal. Furthermore, it would be desirable that such an apparatus be efficient in design, easily adjusted to permit enrichment of the air fuel ratio, and be economical in operation.
Furthermore, it is desirable that there be provided an apparatus by which prior art carburetors can be modified to include a fuel control device of the above type.